The performance of micro-electronic devices has always been limited by the variations found in the dimensions of their critical features, termed critical dimensions or CD. Micro-electronic devices are often manufactured using photo lithographic masks (also referred to as masks or reticles) in a photolithography process. The latter is one of the principal processes in the manufacture of semiconductor devices, and consists of patterning the wafer's surface in accordance with the circuit design of the semiconductor devices to be produced. Such a circuit design is first patterned on a mask. Hence, in order to obtain operating semiconductor devices, the mask must be defect free. Masks are manufactured by a complex process and can suffer from one or more error sources.
Moreover, the mask is often used in a repeated manner to create many dies on the wafer. Thus, any defect on the mask will be repeated multiple times on the wafer and will cause multiple devices to be defective. Establishing a production-worthy process requires tight control of the overall lithography process. Within this process, CD control is a determining factor with respect to device performance and yield.
Various mask inspection tools have been developed and are available commercially. According to the known techniques of designing and evaluating masks, the mask is created and used to expose therethrough a wafer, and then a check is performed to determine whether the features of the mask have been transferred to the wafer according to the design. Any variations in the final features from the intended design necessitate modifying the design, creating a new mask, and exposing a new wafer.
Gridded design rule (GDR) masks were developed in order to facilitate the manufacturing of very small features. GDR masks are also termed single dimensional masks (1D masks) as they include patterns that include parallel lines and spacing between these parallel lines.
There is a need to provide systems and methods for evaluating at least one error source of a mask.